Thermally conductive silicone heat-shrinkable tube

Abstract

The present invention is a thermally conductive silicone heat-shrinkable tube, which is characterized by being a silicone rubber composition that contains: 100 parts by mass of (A) a straight chain organopolysiloxane which has two or more silicon atom-bonded vinyl groups per molecule and has an average degree of polymerization of 3000-50,000, and in which among all substituent groups, 50 mol% or more are methyl groups and 0.05-5.0 mol% are vinyl groups; 5-60 parts by mass of (B) powdered silica having a BET specific surface area of 100 m2 / g or more; 150-2000 parts by mass of (C) one or more types of thermally conductive filler selected from among metals, metal oxides, metal hydroxides, nitrides and carbides; 10-100 parts by mass of (D) a thermoplastic resin; an effective quantity of (E) a curing agent; and an effective quantity of (F) a dispersing agent for a filler. Provided by this configuration is a thermally conductive silicone heat-shrinkable tube which exhibits thermal conductivity and conventional heat-shrinking characteristics.

Description

Thermally Conductive Silicone Heat Shrink Tubing

[0001] The present invention relates to thermally conductive silicone heat shrink tubing.

[0002] Conventionally, heat-shrinkable molded articles have been known which are made by processing silicone rubber compositions in which silicone raw rubber is blended with thermoplastic resins such as polyethylene or silicone resin, and further with fillers, etc. A representative example of such a heat-shrinkable molded article is silicone heat-shrinkable tubing (Patent Document 1).

[0003] LSI chips, such as CPUs, driver ICs, and memories used in electronic devices such as personal computers and mobile phones, generate large amounts of heat as they become more powerful, faster, smaller, and more highly integrated, and the temperature rise caused by this heat can lead to malfunctions or destruction of the LSI chip.For this reason, many heat dissipation methods and heat dissipation members used therefor have been proposed to suppress the temperature rise of LSI chips during operation.

[0004] In the automotive field, conventional automobiles include multiple cables for transmitting power or data signals from one end to the other. However, in recent years, with the increasing performance of electric vehicles and other vehicles, there has been an increasing demand for bus bars that can achieve high voltage and high output in a small space, and there is a need to manage the heat generated during operation (Patent Document 2).

[0005] JP 8-157727 A International Publication No. 2021 / 188438

[0006] Silicone heat-shrinkable tubing is used in a wide range of industrial applications because it can easily cover objects and can be sealed by shrinking when heated. However, its thermal conductivity is insufficient for use in dissipating heat from heat-generating parts such as those mentioned above.

[0007] The present invention has been made to solve the above problems, and has as its object to provide a thermally conductive silicone heat shrinkable tube that has thermal conductivity and conventional heat shrink properties.

[0008] In order to solve the above problems, the present invention provides: (A) 100 parts by mass of a linear organopolysiloxane having two or more vinyl groups bonded to silicon atoms in each molecule and an average degree of polymerization of 3,000 to 50,000, in which 50 mol % or more of all substituents are methyl groups and 0.05 to 5.0 mol % are vinyl groups; (B) a polymerizable composition having a BET specific surface area of ​​100 m ２ / g or more: 5 to 60 parts by mass of powdered silica, (C) at least one or more thermally conductive fillers selected from metals, metal oxides, metal hydroxides, nitrides, and carbides: 150 to 2,000 parts by mass of, (D) a thermoplastic resin: 10 to 100 parts by mass of, (E) a curing agent: an effective amount, and (F) a filler dispersant: an effective amount.

[0009] Such thermally conductive silicone heat shrink tubing has the thermal conductivity and heat shrink properties of conventional heat shrink tubing.

[0010] In the thermally conductive silicone heat-shrinkable tubing of the present invention, the component (D) is preferably an organopolysiloxane resin.

[0011] Such a thermally conductive silicone heat-shrinkable tube becomes a molded product that retains its heat-shrinkability.

[0012] Furthermore, in the thermally conductive silicone heat-shrinkable tubing of the present invention, the component (C) is preferably one or more selected from the group consisting of pulverized aluminum nitride, spherical alumina, and pulverized alumina.

[0013] Such thermally conductive silicone heat shrink tubing has excellent thermal conductivity.

[0014] Furthermore, the thermally conductive silicone heat-shrinkable tubing of the present invention preferably has a thermal conductivity of 0.5 (W / m·K) or more.

[0015] Such thermally conductive silicone heat shrink tubing has excellent thermal conductivity.

[0016] The thermally conductive silicone heat-shrinkable tubing of the present invention preferably contains 3 to 100 parts by mass of the above-mentioned component (F).

[0017] Such a thermally conductive silicone heat-shrinkable tube has excellent thermal conductivity because the thermally conductive filler is uniformly dispersed in a matrix made of organopolysiloxane.

[0018] The thermally conductive silicone heat shrinkable tubing of the present invention further comprises, as component (G), a silicone rubber having a BET specific surface area of ​​50 to 400 m ２ It is preferable that the composition contains 5 to 300 parts by mass of an inorganic filler other than the components (B) and (C) in an amount of 100 to 1500 parts by mass / g.

[0019] Such a thermally conductive silicone heat shrinkable tube has excellent physical strength.

[0020] The thermally conductive silicone heat-shrinkable tubing of the present invention can be used as a covering material for bus bars that are connected to switchboards, control panels, or batteries and conduct large amounts of current.

[0021] Such thermally conductive silicone heat-shrinkable tubing makes it possible to create a bus bar that can achieve high voltage and high output in a small space.

[0022] The thermally conductive silicone heat shrinkable tube of the present invention can also be used to cover the heat generating parts of transistors or semiconductor devices.

[0023] Such a thermally conductive silicone heat shrink tube can suppress the temperature rise of a transistor or semiconductor device during operation.

[0024] As described above, the thermally conductive silicone heat shrink tubing of the present invention has the thermal conductivity and the heat shrinkage properties of conventional heat shrink tubing, and can be used as a heat dissipation member for suppressing the temperature rise of LSI chips during operation, or as a covering material for bus bars that can achieve high voltage and high output in a small space.

[0025] As described above, there has been a need for the development of a silicone heat-shrinkable tube with high thermal conductivity.

[0026] As a result of extensive research into the above-mentioned problems, the present inventors discovered that a thermally conductive silicone heat-shrinkable tubing with high thermal conductivity can be developed by applying a silicone rubber composition containing the following (A) vinyl group-containing linear organopolysiloxane, (B) powdered silica, (C) thermally conductive filler, (D) thermoplastic resin, (E) curing agent, and (F) filler dispersant, and thus completed the present invention.

[0027] That is, the present invention provides: (A) 100 parts by mass of a linear organopolysiloxane having two or more vinyl groups bonded to silicon atoms in each molecule and an average degree of polymerization of 3,000 to 50,000, in which 50 mol % or more of all substituents are methyl groups and 0.05 to 5.0 mol % are vinyl groups; (B) a BET specific surface area of ​​100 m ２ / g or more: 5 to 60 parts by mass of powdered silica, (C) at least one or more thermally conductive fillers selected from metals, metal oxides, metal hydroxides, nitrides, and carbides: 150 to 2,000 parts by mass of, (D) a thermoplastic resin: 10 to 100 parts by mass of, (E) a curing agent: an effective amount, and (F) a filler dispersant: an effective amount.

[0028] The present invention will be described in detail below, but the present invention is not limited thereto.

[0029] [Component (A)] Component (A) is a linear organopolysiloxane having two or more vinyl groups bonded to silicon atoms per molecule and an average degree of polymerization of 3,000 to 50,000, in which at least 50 mol % of all substituents are methyl groups and 0.05 to 5.0 mol % are vinyl groups.

[0030] The component (A) is the main component of the silicone rubber composition that constitutes the silicone heat-shrinkable tubing of the present invention.

[0031] The organopolysiloxane has at least two, preferably 2 to 10,000, vinyl groups bonded to silicon atoms in one molecule.

[0032] Examples of substituents other than vinyl groups on the organopolysiloxane include alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aryl groups such as phenyl and tolyl; and aralkyl groups such as benzyl and 2-phenylethyl. Of these, methyl and phenyl groups are preferred.

[0033] Of all the substituents on the organopolysiloxane, 50 mol % or more, preferably 80 to 95 mol %, are methyl groups, and more preferably, all the substituents other than vinyl groups are methyl groups.Furthermore, of all the substituents on the organopolysiloxane, 0.05 to 5.0 mol %, preferably 0.1 to 3.0 mol % are vinyl groups.

[0034] The average degree of polymerization of the organopolysiloxane is 3,000 to 50,000, and preferably 4,000 to 20,000. The average degree of polymerization in the present invention is a value determined from the weight average molecular weight determined by gel permeation chromatography (GPC) analysis measured under the conditions shown below, using polystyrene of known molecular weight as a standard substance.

[0035] [Measurement conditions] Developing solvent: tetrahydrofuran (THF) Flow rate: 0.6 mL / min Detector: differential refractive index detector (RI) Column: TSK Guard column Super H-H TSKgel Super H4000 (6.0 mm I.D. × 15 cm × 1) TSKgel Super H3000 (6.0 mm I.D. × 15 cm × 1) TSKgel Super H2000 (6.0 mm I.D. × 15 cm × 1) (all manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 50 μL (THF solution with a concentration of 2.0% by mass)

[0036] The kinematic viscosity of this linear organopolysiloxane is 1,000 mm at 25°C as measured using a Cannon-Fenske viscometer as described in JIS Z8803:2011. ２ / s or more, and 100,000 to 10,000,000 mm ２ It is more preferable that the ratio is / s.

[0037] [Component (B)] Component (B) is a sintered body having a BET specific surface area of ​​100 m ２ The powdered silica has a BET specific surface area of ​​100 m / g or more, which has been conventionally used for silicone rubber. ２ / g or more, or powdered silica such as fumed silica, crystalline silica (dry silica), precipitated silica (wet silica), or powdered silica whose surface has been hydrophobized with silane, silazane, siloxane, etc. The upper limit of the BET specific surface area of ​​component (B) is not particularly limited, but may be, for example, 400 m ２ The BET specific surface area is a value measured by the BET method (nitrogen adsorption method).

[0038] The blend amount of component (B) is 5 to 60 parts by mass, and preferably 10 to 40 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). If the blend amount is less than 5 parts by mass, the strength required for stretching cannot be obtained, and if the blend amount is more than 60 parts by mass, the physical properties such as elongation required for stretching may not be obtained.

[0039] [Component (C)] Component (C) is a thermally conductive filler, and examples thereof include metal oxides such as aluminum oxide, zinc oxide, magnesium oxide, titanium oxide, and beryllium oxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, nitrides such as aluminum nitride, silicon nitride, and boron nitride, carbides such as boron carbide, titanium carbide, and silicon carbide, graphite and other graphite, metals such as aluminum, copper, nickel, and silver, and mixtures thereof. In particular, when electrical insulation is required for the silicone rubber composition of the present invention, metal oxides, metal hydroxides, nitrides, or mixtures thereof are preferred, and amphoteric hydroxides or amphoteric oxides are also acceptable, and specifically, it is preferred to use one or more selected from the group consisting of aluminum hydroxide, boron nitride, aluminum nitride, zinc oxide, aluminum oxide, magnesium oxide, and magnesium hydroxide.

[0040] Aluminum oxide, aluminum hydroxide, magnesium oxide, magnesium hydroxide, zinc oxide, aluminum nitride, and boron nitride are insulating materials, have relatively good compatibility with component (A), are available in a wide industrial range of particle sizes, are readily available, and are available at relatively low cost, and therefore are suitable as thermally conductive inorganic fillers.

[0041] Furthermore, in the thermally conductive silicone heat-shrinkable tubing of the present invention, component (C) is preferably one or more selected from the group consisting of pulverized aluminum nitride, spherical alumina, and pulverized alumina, and such thermally conductive silicone heat-shrinkable tubing has excellent thermal conductivity.

[0042] The average particle size of component (C) is preferably 0.1 to 300 μm, and more preferably 1 to 200 μm. When the average particle size is in the range of 0.1 to 300 μm, a silicone rubber composition with the desired high thermal conductivity can be obtained, and the resulting silicone rubber composition has excellent extensibility and is easy to mold, and is easily dispersed uniformly with other thermally conductive fillers, thereby providing a sufficient effect of increasing thermal conductivity.

[0043] In the present invention, the average particle size is the value of the cumulative 50% particle size (D50) on a volume basis measured by a particle size distribution measuring device MT3000II manufactured by Microtrac Bell.

[0044] The amount of component (C) is preferably 150 to 2,000 parts by mass, more preferably 300 to 1,000 parts by mass, per 100 parts by mass of the polyorganopolysiloxane of component (A). If the amount of the thermally conductive filler is less than 150 parts by mass, the thermal conductivity of the silicone rubber layer is likely to be insufficient. On the other hand, if the amount of the thermally conductive filler is more than 2,000 parts by mass, it may be difficult to uniformly incorporate the filler into the composition, which may result in poor moldability.

[0045] [Component (D)] Component (D) is a thermoplastic resin and may be the same as those used in known silicone heat-shrinkable tubing, examples of which include methyl methacrylate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, and various thermoplastic silicone resins, etc. In consideration of miscibility with the silicone resin, component (D) is preferably an organopolysiloxane resin, and more preferably an organopolysiloxane resin represented by the following formula (1):

[0046] The amount of thermoplastic resin (D) blended is 10 to 100 parts by mass, and more preferably 20 to 60 parts by mass, per 100 parts by mass of organopolysiloxane (A). If the blended amount is less than 10 parts by mass, a molded product having the desired heat shrinkability cannot be obtained, while if the blended amount is more than 100 parts by mass, a product having raw rubber elasticity cannot be obtained.

[0047] [Component (E)] Component (E) is a curing agent (crosslinking agent and / or curing catalyst), and any of the conventionally known agents typically used for curing silicone rubber can be used. For example, when curing by a radical reaction, organic peroxides such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide are used. When curing by an addition reaction, an addition reaction crosslinker consisting of a combination of an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule and a platinum catalyst such as platinum element or chloroplatinic acid is used.

[0048] The amount of component (E) added is typically 0.1 to 3 parts by mass of peroxide per 100 parts by mass of organopolysiloxane in the case of a radical reaction, and in the case of an addition reaction, the amount of organohydrogenpolysiloxane added is preferably an amount that satisfies the molar ratio of silicon-bonded hydrogen atoms (SiH groups) to vinyl groups (SiVi) in component (A) SiH / SiVi = 0.5 to 5, and the amount of platinum catalyst added is preferably 0.1 to 2,000 ppm as platinum metal.

[0049] [Component (F)] Component (F) is a filler dispersant that, when mixed with the above components in a commonly used mixer such as a twin-roll mill, kneader, or Banbury mixer, contains a low-molecular-weight siloxane, alkoxysilane, silazane, or diphenylsilanediol, both ends of which are capped with hydroxyl groups, or a dimethylpolysiloxane having a trialkoxysilyl group at one end of the molecular chain, as represented by the following formula (2), to facilitate uniform mixing as needed. Component (F) functions as a surface treatment agent for uniformly dispersing the thermally conductive filler (C) in the matrix composed of the organosiloxane (A) during the preparation of the silicone rubber composition of the present invention.

[0050] In formula (2), R ５ are each independently an alkyl group having 1 to 6 carbon atoms, and c is an integer from 5 to 100. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group. ５ is preferably an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, or a propyl group, and more preferably a methyl group.

[0051] The blending amount of component (F) is preferably 3 to 100 parts by mass, more preferably 5 to 50 parts by mass, and even more preferably 10 to 30 parts by mass per 100 parts by mass of component (A). Blending within the range of 3 to 100 parts by mass allows the thermally conductive filler to be uniformly dispersed within the matrix composed of the organopolysiloxane. Furthermore, blending within the range of 3 to 100 parts by mass does not induce oil separation, and sufficient wettability between the organopolysiloxane and the thermally conductive filler is achieved, resulting in the formation of a silicone rubber composition.

[0052] [Other Components] [(G) Inorganic Filler] In addition to the components (A) to (F) above, the thermally conductive silicone heat-shrinkable tubing of the present invention further comprises, as component (G), an inorganic filler having a BET specific surface area of ​​50 to 400 m ２ / g of an inorganic filler other than the components (B) and (C).

[0053] The inorganic filler of component (G) has a specific surface area of ​​50 to 400 m2 as measured by the BET method. ２ / g, and 100 to 350m ２ / g is more preferable. ２ When the content is in the range of 1 / g, the reinforcing effect is sufficiently exhibited, the physical strength of the thermally conductive heat-shrinkable tube is sufficient, and the production thereof is also easy.

[0054] The blending amount of component (G) is preferably 5 to 300 parts by mass, and more preferably 20 to 200 parts by mass, per 100 parts by mass of component (A). When the blending amount is in the range of 5 to 300 parts by mass, sufficient rubber strength is obtained and blending is easy.

[0055] The inorganic filler component (G) is not particularly limited as long as it is different from the finely powdered silica component (B) and the thermally conductive filler component (C). For example, inorganic fillers such as fumed silica, crystalline silica, precipitated silica, silsesquioxane, fumed titanium dioxide, magnesium oxide, zinc oxide, iron oxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate, layered mica, carbon black, diatomaceous earth, glass fiber, titanium white, quartz powder, and talc are listed, among which crystalline silica, precipitated silica, and titanium white are preferably used. In addition, these fillers may be surface-treated with organosilicon compounds such as organoalkoxysilane compounds, organochlorosilane compounds, organosilazane compounds, and low-molecular-weight siloxane compounds.

[0056] In addition to the components (A) to (G) above, the thermally conductive silicone heat-shrinkable tubing of the present invention can contain optional components such as deterioration inhibitors, heat resistance improvers, heat resistance agents such as titanium oxide and cerium oxide, internal mold release agents such as zinc stearate and dimethyl silicone oil, and pigments, in any desired proportions.

[0057] The thermally conductive silicone heat-shrinkable tubing of the present invention can be obtained by molding the silicone rubber composition into a tubular shape, vulcanizing it, and then heating and stretching it in the radial direction (i.e., expanding it). In this case, the silicone rubber composition is preferably extruded into a tubular shape at a drawdown ratio of 150% to 250%, and more preferably 170% to 200%, relative to the nipple diameter.

[0058] The vulcanization conditions are appropriately selected depending on the curing method, but in the present invention, a method of heat curing at a temperature of 100° C. or higher at normal pressure is adopted. Further, this tubular molded article is stretched in the radial direction under heating at 120 to 220° C., and then cooled in that state to obtain a heat-shrinkable tubular molded article.

[0059] The silicone heat-shrinkable tube thus obtained shrinks almost completely to its original shape when heated to 120° C. or higher by hot air or other heating means.

[0060] The thermally conductive silicone heat shrink tubing of the present invention preferably has a thermal conductivity of 0.5 (W / m·K) or more. Such thermally conductive silicone heat shrink tubing has excellent thermal conductivity and can be used as a heat dissipation component to suppress temperature rise in operating LSI chips, or as a covering material for bus bars that can achieve high voltage and high output in a small space. The upper limit of the thermal conductivity of the thermally conductive silicone heat shrink tubing of the present invention is not particularly limited, but can be, for example, 20 (W / m·K) or less.

[0061] The thermal conductivity is measured using a thermal conductivity meter in accordance with ISO22007-2:2008.

[0062] The thermally conductive silicone heat-shrinkable tubing of the present invention can be used as a covering material for bus bars that are connected to switchboards, control panels, or batteries and conduct large amounts of current, enabling bus bars to achieve high voltage and high output in a small space.

[0063] The thermally conductive silicone heat shrink tubing of the present invention can be used to cover the heat-generating parts of transistors or semiconductor devices, thereby suppressing the temperature rise of the transistors or semiconductor devices during operation.

[0064] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0065] [Example 1] 100 parts by mass of dimethylpolysiloxane (average degree of polymerization: 6,000) having 0.4 mol% of vinyl groups, with both molecular chain terminals blocked with dimethylvinylsilyl groups, based on the total amount of monovalent hydrocarbon groups, was used as component (A). ２ 25 parts by mass of fumed silica (average degree of polymerization 8,000) having a molecular weight of 1 / g, 250 parts by mass of aluminum oxide having an average particle size of 4 μm as component (C-1), 75 parts by mass of aluminum oxide having an average particle size of 1 μm as component (C-2), 50 parts by mass of a methylphenylpolysiloxane resin represented by the following formula (1) as component (D), and 15 parts by mass of dimethylpolysiloxane having an average degree of polymerization of 30 and one end capped with a trimethoxysilyl group as component (F) represented by the following formula (3) were mixed in a kneader, and a compound was produced using a twin roll mill. 100 parts by mass of the resulting compound was mixed with 0.02 parts by mass of a 5% solution of chloroplatinic acid in 2-ethylhexanol as component (E-1) and 1.4 parts by mass of a linear dimethylsiloxane-methylhydrogensiloxane copolymer (hydrosilyl group content: 0.0076 mol / g) as component (E-2), the copolymer having both molecular chain terminals blocked with trimethylsiloxy groups, an average degree of polymerization of 40, an average of 20 hydrosilyl groups per molecule, and a viscosity of 20 mPa s. The resulting silicone rubber composition was molded into a sheet, press-cured at 120°C for 10 minutes, and then post-cured at 200°C for 4 hours to allow it to harden.

[0066] The cured sheet was then stretched to 2 times its original size at 200°C, cooled to room temperature, and the stress was removed. The thermal conductivity, stretch retention, and heat shrinkage of the cured sheet were then measured. The results are shown in Table 1.

[0067] Example 2 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the formulation of the thermally conductive filler (C), component (C) used in Example 1, was changed to 330 parts by mass of aluminum oxide having an average particle size of 4 μm for component (C-1) and 100 parts by mass of aluminum oxide having an average particle size of 1 μm for component (C-2). The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 1.

[0068] Example 3 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the formulation of the thermally conductive filler (C), component (C) used in Example 1, was changed to 200 parts by mass of aluminum oxide having an average particle size of 4 μm as component (C-1) and 60 parts by mass of aluminum oxide having an average particle size of 1 μm as component (C-2). The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 1.

[0069] Example 4 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the blending amount of the methylphenylpolysiloxane resin (component (D)) used in Example 1 was changed to 65 parts by mass. The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 1.

[0070] Example 5 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the amount of filler dispersant (component (F)) used in Example 1 was changed to 24 parts by mass. The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 1.

[0071] Comparative Example 1 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the formulation of the thermally conductive filler (C), component (C), used in Example 1 was changed to 100 parts by mass of aluminum oxide having an average particle size of 4 μm for component (C-1) and 30 parts by mass of aluminum oxide having an average particle size of 1 μm for component (C-2). The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 2.

[0072] Comparative Example 2 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the methylphenylpolysiloxane resin (component (D)) used in Example 1 was not added. The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 2.

[0073] Comparative Example 3 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the amount of methylphenylpolysiloxane resin (component (D)) used in Example 1 was changed to 5 parts by mass. The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 2.

[0074] Comparative Example 4 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the amount of methylphenylpolysiloxane resin (component (D)) used in Example 1 was changed to 150 parts by mass. The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 2.

[0075] Comparative Example 5 A cured sheet was produced using the same formulation and molding conditions as in Example 1, except that the filler dispersant (F), used in Example 1, was not added. The thermal conductivity, elongation retention, and heat shrinkage of the resulting cured sheet were measured. The results are shown in Table 2.

[0076] [Method for Evaluating Silicone Rubber Compositions] (1) Thermal Conductivity The obtained silicone rubber composition was press-molded into a 6 mm thick sheet using a 60 mm x 60 mm x 6 mm mold at 120°C for 10 minutes, adjusting the pressure so that the thickness after curing was 6 mm. The composition was cured into a 6 mm thick sheet. Using a thermal conductivity meter (TPS-2500S, product name of Kyoto Electronics Manufacturing Co., Ltd.), a probe was sandwiched between two sheets and the thermal conductivity of the sheet was measured in accordance with ISO 22007-2:2008. (2) Stretch Retention Rate The stretch retention rate was evaluated as "Good" if the obtained cured sheet could withstand 200% stretching after being placed in a jig and maintained a stretch retention rate of 60% or more after removal from the jig. (3) Heat Shrinkage Rate The heat shrinkage rate was evaluated as "Good" if the obtained cured sheet was heated at 100°C for 3 minutes and maintained a heat shrinkage rate of 50% or more.

[0077] The stretch retention rate and heat shrinkage rate were calculated by the following formulas. L0: Original length of the gauge line L1: Length between the gauge lines when heated to 200°C, stretched 200%, and fixed to the jig L2: Length between the gauge lines when removed from the jig L3: Length between the gauge lines after removing from the jig, heating at 100°C for 3 minutes, and cooling

[0078]

[0079]

[0080] The results in Table 1 demonstrate that the cured sheets (Examples 1-5) obtained from the silicone rubber compositions of the present invention have good thermal conductivity and exhibit stretch retention and heat shrinkage properties sufficient for use as heat-shrinkable molded articles. On the other hand, the results of Comparative Example 1 demonstrate that when the blending amount of component (C) is less than 150 parts by mass, the cured sheets exhibit poor thermal conductivity. Furthermore, the results of Comparative Examples 2-4 demonstrate that unless the blending amount of component (D) is within the range of 10 to 100 parts by mass, the stretch retention and heat shrinkage properties sufficient for use as heat-shrinkable molded articles cannot be obtained. Furthermore, the results of Comparative Example 5 demonstrate that unless the blending amount of component (F) is within the range of 3 to 100 parts by mass, the silicone rubber composition of the present invention cannot be formed.

[0081] From the above, it was found that the thermally conductive silicone heat shrink tubing of the present invention has the thermal conductivity and heat shrink properties of conventional heat shrink tubing, and can be used as a heat dissipation material to suppress the temperature rise of LSI chips during operation, or as a covering material for bus bars that can achieve high voltage and high output in a small space.

[0082] This specification encompasses the following embodiments: [1]: (A) 100 parts by mass of a linear organopolysiloxane having two or more vinyl groups bonded to silicon atoms per molecule and an average degree of polymerization of 3,000 to 50,000, in which 50 mol % or more of all substituents are methyl groups and 0.05 to 5.0 mol % are vinyl groups; (B) 100 parts by mass of a linear organopolysiloxane having a BET specific surface area of ​​100 m ２ A thermally conductive silicone heat shrinkable tube characterized by being a silicone rubber composition containing: (a) 5 to 60 parts by mass of powdered silica having a viscosity of 1 / g or more; (C) 150 to 2,000 parts by mass of at least one thermally conductive filler selected from metals, metal oxides, metal hydroxides, nitrides, and carbides; (D) 10 to 100 parts by mass of a thermoplastic resin; (E) an effective amount of a curing agent; and (F) an effective amount of a filler dispersant. [2]: The thermally conductive silicone heat shrinkable tube described in [1] above, wherein component (D) is an organopolysiloxane resin. [3]: The thermally conductive silicone heat shrinkable tube described in [1] or [2] above, wherein component (C) is one or more selected from crushed aluminum nitride, spherical alumina, and crushed alumina. [4]: ​​The thermally conductive silicone heat shrinkable tube described in any one of [1], [2], or [3] above, wherein the thermal conductivity is 0.5 (W / m·K) or more. [5]: The thermally conductive silicone heat-shrinkable tubing according to any one of [1] to [4] above, characterized in that it contains 3 to 100 parts by mass of the component (F). [6]: It further contains, as component (G), a silicone rubber composition having a BET specific surface area of ​​50 to 400 m ２

[0023] The thermally conductive silicone heat shrinkable tubing according to any one of [1] to [5] above, characterized in that it contains 5 to 300 parts by mass of an inorganic filler other than components (B) and (C), with a mass of 1000 to 10 ...

[0083] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. (A) 100 parts by mass of a linear organopolysiloxane having two or more vinyl groups bonded to silicon atoms per molecule, an average degree of polymerization of 3,000 to 50,000, in which 50 mol % or more of all substituents are methyl groups and 0.05 to 5.0 mol % are vinyl groups; (B) a BET specific surface area of ​​100 m ２ / g or more: 5 to 60 parts by mass of powdered silica, (C) at least one or more thermally conductive fillers selected from metals, metal oxides, metal hydroxides, nitrides, and carbides: 150 to 2,000 parts by mass of, (D) a thermoplastic resin: 10 to 100 parts by mass of, (E) a curing agent: an effective amount, and (F) a filler dispersant: an effective amount.

2. The thermally conductive silicone heat-shrinkable tubing according to claim 1, wherein component (D) is an organopolysiloxane resin.

3. A thermally conductive silicone heat-shrinkable tube according to claim 1 or 2, characterized in that component (C) is one or more selected from the group consisting of pulverized aluminum nitride, spherical alumina and pulverized alumina.

4. The thermally conductive silicone heat-shrinkable tube according to claim 1, characterized in that it has a thermal conductivity of 0.5 (W / m·K) or more.

5. The thermally conductive silicone heat-shrinkable tubing according to claim 1, characterized in that it contains 3 to 100 parts by mass of component (F).

6. Furthermore, as component (G), a BET specific surface area of ​​50 to 400 m ２ 2. The thermally conductive silicone heat-shrinkable tube according to claim 1, further comprising 5 to 300 parts by mass of an inorganic filler other than components (B) and (C), in an amount of 0.1 to 0.5 parts by mass / g.

7. The thermally conductive silicone heat-shrinkable tubing according to claim 1, which is used as a covering material for bus bars that are connected to a distribution board, a control panel, or a battery and conduct large amounts of current.

8. The thermally conductive silicone heat-shrinkable tube according to claim 1, which is used to cover the heat-generating parts of a transistor or semiconductor device.

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